This invention relates to marine seismic exploration and, more particularly, to a marine seismic streamer configured to reduce tow noise on the recorded seismic data by employing spacers with variable apertures, along the length of the streamer.
In conducting a marine seismic survey, a seismic energy source is employed by an exploration vessel to generate a seismic signal, referred to as a seismic pressure wave, which is transmitted through the water layer into the subsurface formations. A portion of the signal is reflected from the subsurface reflecting interfaces back to the water layer where it is received by a seismic streamer being towed behind the exploration vessel. The streamer is comprised of a plurality of hydrophones which generate electrical signals in response to the received seismic signals. The hydrophones are spread along the length of the streamer and are electrically connected through the streamer to seismic recording instruments on board the exploration vessel. Such a marine seismic survey may be typically carried out with the exploration systems of the type described in U.S. Pat. No. 4,146,870 to W. H. Ruehle and U.S. Pat. No. 4,581,724 to R. G. Zachariadis wherein a seismic energy source and seismic streamer are towed through the water along a line of exploration.
In seismic marine operations numerous problems are encountered in the recording of seismic data that are not encountered during land operations. A primary one of these problems is tow noise generated by both the movement of the vessel and the streamer through the water as they traverse along the line of exploration.
It is, therefore, a primary object of the present invention to provide for a seismic streamer that can discriminate against such tow noise and thereby provide seismic signals with less distortion, more dynamic range, and broader frequency spectrum than provided by conventional seismic streamers. Seismic signals with lower distortion and broader dynamic range will resolve thin beds and stratigraphic traps more readily. Reducing noise will permit detection of deeper events and better resolution of events at all levels.